Glendale - It wasn't just Justin Bieber's fans who had "Bieber Fever" as the teen idol kicked off his national Believe tour in Glendale, Arizona.
Video posted on YouTube shows the pop music star vomiting twice on stage on Saturday night during his sold-out concert at the Jobing.com Arena. He left the stage after each episode, but returned and even did an encore.
KTVK-TV reported Bieber's fans sang some of his songs while he was offstage and he later apologised for being sick.
Bieber later tweeted "Great show. Getting better for tomorrow's show !!!! Love u"
He later added: "And .... Milk was a bad choice!"
Bieber's 45-city Believe tour continues at the MGM Grand Garden Arena in Las Vegas.